毕节杨家湾地区水土流失与地层岩性关系的初步探讨

A Preliminary Discussion on the Relations Between Soli Erosion and Stratigraphic Lithologic Features of Yangjiawan Area in Bijie, Guizhou

本文简要介绍长江上游贵州境内的乌江流域水土流失概况,着重叙述乌江上游六冲河流域内的毕节县杨家湾地区影响水土保持的重要因素在于地层岩性的分布,水土流失的强弱与岩石的组合及地形坡度有着必然的相关性,提出了本地区应首先治理T_1f分布区的看法,供水土保持工作者参考。

The soil erosion of Ouizhou is very serious. Only Wu River carries away 19, 900, 000 tons of sand every year, this amount equivalent to a loss of 40,000 tons of nitrogen fertilizer and 30,000 tons of phosphate fertilizer according to the calculation of general soil nutrient continent of Guizhou. The mud and sand in Wu River mainly comes from Liuchong River in the upper reaches, which carry away 800 tons/km2 of sand every year, the amount being about 2. 5 times as much as that carried away by the middle reaches of Wu River. The main reason causing this phenomenon Is closely related to the distribution of the stratigraphic lithologic features. The strata of the middle and upper reaches of the Liuchong River Valley are mainly Feixianguan group of Lower Triassic series and basalt of Emei Mountain and Xuanwei - Wangjiuzai groups of Upper Permian series. These stratigraphic rocks form soil blocks with abundant useful compositions, easily cultivated and easily planted. So the opening up of steep slopes is very serious, especially the rate of cultivating of Feixianguang group is up to more than 65%. The soil structures of these strata are porous, with many slopes and gullies in the same direction, causing soil erosion to be more serious This area should be protected and harnessed. First, the cultivated steep slopes >25°) and the barren land should be again used for forests instead of being cultivated, and arborous trees and frutices should be planted in a planned way. The state support and the harnessing of this large area should be combined to quicken the harnessing steps and to strengthen the harnessing effect.